Retraction notice to “Use of LiDAR for Calculating Solar Irradiance on Roofs and Façades of Buildings at City Scale: Methodology, Validation, and Analysis” [ISPRS Journal of Photogrammetry and Remote Sensing – 138 (2018)12-29] - Cheng, Liang; Xu, Hao; Li, Shuyi; Chen, Yanming; Zhang, Fangli; Li, Manchun (ISPRS journal of photogrammetry and remote sensing, 2018)